1. Field of the Invention
The present invention relates to a method used in a communication device in a wireless communication system, and more particularly, to a method of updating network detection and selection information and traffic routing information.
2. Description of the Prior Art
3GPP in Release 11 proposes Access Network Discovery and Selection Function (ANDSF) Management Object (MO) to manage Inter-System Mobility Policy (ISMP) and Inter-System. Routing Policy (ISRP) as well as access network discovery information stored in a user equipment (UE) supporting provisioning of such information from an ANDSF, which is a network element providing access network (e.g. WLAN) discovery and selection assistance data as per operators' policy. In a word, ANDSF provides information containing network detection and selection information and traffic routing information to assist the UE with selecting the access network or the inter-system mobility policy to control and assist the UE with performing the inter-system change or to assist the UE with determining how to route IP traffics or all of the above mentioned. This information also contains ISMP, which prioritizes the access network when the UE is not capable to connect to the EPC through multiple accesses, and ISRP, which indicates how to distribute traffic among available accesses when the UE is capable to connect to the EPC through multiple accesses while access network discovery and selection information provides further information for the UE to access the access network defined in the ISMP or in the ISRP or in the access network discovery information.
Please refer to FIG. 1, which illustrates ANDSF operation according to the prior art. The ANDSF of Public Land Mobile Network (PLMN) sends ANDSF MO indicating a preferred Service Set Identifier (SSID) for identifying a WLAN or a priority of SSIDs, to the UE. The UE determines whether to use a WLAN according to the information (i.e. SSID) obtained from the ANDSF MO kept in the UE. For example, when the UE moves into the service coverage of a WLAN, the UE could be aware of the existing of the WLAN by a SSID broadcasted by the WLAN AP (Access Point). If the broadcasted SSID is the SSID indicated in the ANDSF MO, the UE selects the WLAN. Note that, ANDSF rules (including ISRP/ISMP) may be provided to the UE via the ANDSF MO or pre-configured at the UE.
Please refer to FIG. 2, which illustrates ANDSF rules supporting RAN assistance information. The eNB provides RAN assistance information to the UE, wherein the RAN assistance information includes parameters and/or values, such as threshRsrpLow=−90 dBm, threshRsrpHigh=−80 dbm, threshRsrqLow=3 dB, threshRsrqHigh=4 dB, etc. The UE applies the parameters as well as the values associated to specific parameters of RAN assistance information to ANDSF rules (including IARP rule, ISMP rule, ISRP rule, etc) obtained via the ANDSF MO or via existing OMA-DM mechanisms or pre-configured at the UE. In a word, when the UE receives RAN assistance information, this information is taken into account for evaluating the provisioned ANDSF rules.
However, RAN assistance information could be different or out-of-date when the UE changes serving RAN access node (e.g. a serving eNB). In addition, RAN rules could be different when the device changes serving PLMN or serving RAN access node. In detail, please refer to FIG. 3, which illustrates that the UE supporting ANDSF operation moves from the source cell to the target cell. In case the source cell and the target cell belong to different PLMNs, the mobility of the UE may also bring out the change of PLMN. Therefore, the applicant notices that a mechanism is needed to provide and to update RAN rules and RAN assistance information to the UE.
In addition, RAN assistance information could be updated frequently to reflect the RAN condition, or RAN rules should be update to the UE efficiently for better user experience and load balancing. However, RAN assistance information or RAN rules update could be cumbersome so that the delivery of RAN assistance information or RAN rules could consume a lot of radio resource. Therefore, the applicant believes a mechanism is needed to provide reduced amount of data sent from access node to the UE.